1. Field of the Invention
The present invention relates to a roll screen, particularly to a roll screen in which a winding speed of the screen can be decreased.
2. Description of the Related Art
A conventional roll screen has been disclosed in, for example, Published Unexamined Utility Model Application No. 26316 of 1983(Showa 58).
This screen comprises a static screw which is securely arranged on a rotating axis for a winding pipe of a screen, a moving couple which is moved along the static shaft together with the rotation of the winding pipe, and a hydraulic damper mounted in the winding pipe. The hydraulic damper is provided with a piston rod and a piston which are moved in an axial direction together with the moving coupler, a cylinder secured to the winding sleeve, and oil filled in the cylinder. When the oil in the hydraulic damper is pressed by the piston rod moved together with the winding of the screen, a winding speed of the screen is decreased.
In the screen provided the above described brake mechanism, since the winding damper is always operated during the winding of the screen except a starting stage of the winding of the screen, a winding speed of the screen is decreased after the starting stage. In a final stage of the winding of the screen, since the winding diameter of the screen already wound becomes larger and a weight of a screen to be wound is reduced, a winding speed cannot be well controlled. Therefore, there is a problem that when the screen is completely wound, a crashing sound caused by a weight bar attached at the bottom of the screen is generated, and an impulse force is excessively increased.
Further, in the above described roll screen, the hydraulic damper is always operated even if the screen is wound from the intermediate position in a vertical direction and a winding speed of the screen is not so fast in a final stage of the winding of the screen. If the winding speed of the screen is so decreased to excess by the hydraulic damper, the screen cannot be wound to the end.
Further, in the above described roll screen, a winding speed of the screen is also decreased in the rewinding of the screen because an oil flow is always generated in the hydraulic damper. Therefore, there is a problem that if more than one brake means same as the above were mounted in the winding pipe to operate together, a winding speed of the screen would be decreased to excess in the rewinding of the screen, and its operation would become bad.
The present invention was made in consideration of the above-described problems. An object of the invention is to provide a roll screen in which a crashing sound and an impulse force caused by a weight bar in a final stage of the winding of the screen can be relieved.
Other object of the invention is to provide a roll screen in which the winding speed of the screen is not so decreased that the screen can still be wound to the end.
Further object of the invention is to provide a roll screen in which a winding speed of the screen can be decreased only in a final stage of winding.
To achieve the above-mentioned objects, in a roll screen according to the present invention, a spring is mounted within a winding pipe rotatably supported on side plates and a screen is wound on the winding pipe by an accumulated force of the spring. A brake is mounted in the winding pipe to decrease a winding speed of the screen only from a final stage of the winding of the screen.
Since a winding speed of the screen is decreased from the final stage of the winding of the screen, it is possible to relieve a crashing sound and an impulse force in a final stage of the winding of the screen.
Preferably, a second brake can be mounted in the winding pipe for decreasing a winding speed of the screen from a starting stage of the winding of the screen. Thereby, a screen can be decreased effectively by the operation of the two brakes.
Alternatively, the roll screen according to the present invention can be formed in such a manner that the brake can decrease a winding speed of the screen only when a winding speed of the screen is more than a given level. Thereby, the winding speed of the screen is not so excessively decreased that the screen can be still wound to the end.
The roll screen according to the present invention may be formed in such a manner that the brake comprises a screw shaft fixedly supported on the side plate, a clutch case which is mounted in the winding pipe so as to be movable in the axial direction but unrotatable relative to the winding pipe and which can be moved along the screw shaft together with rotating of the winding pipe, and a brake section disposed on an end side of the screw shaft. The clutch case is engaged with the brake section from a final stage of the winding of the screen to operate the brake section. The roll screen according to the present invention may be formed in such a manner that the brake section can further comprise a rotary brake and a brake case which houses the rotary brake and has a brake pin which extends in the axial direction toward the clutch case. When the clutch case is engaged with the brake pin, the rotary brake is rotated to operate. The winding speed of the screen can be surely decreased only when in a final stage of the winding of the screen, since the clutch case is moved along the screw shaft to be engaged with the brake section in the final stage of the winding of the screen.
Further, the roll screen according to the present invention may be formed in such a manner that the clutch case comprises a clutch piece having one end side rotatably attached to a body of the clutch case and another end side provided with an engaging portion to be engaged with the brake pin, a spring which always pushes the another end side of the clutch piece toward an outside of the clutch case. The engaging portion can be engaged with the brake pin only when the clutch case is rotating in the direction of the winding of the screen. Thereby, when the clutch case is rotating in the rewinding direction, the brake does not operate, since the clutch piece is swingable to dodge to the inside of the clutch case so as to escape from the brake pin against the spring. Therefore, the winding speed of the screen can decreased only when the clutch case is rotating in the winding direction of the screen.
Alternatively, the roll screen according to the present invention may be formed in such a manner that the clutch case comprises a clutch piece having one end side rotatably attached to a body of the clutch case and another end side provided with an engaging portion to be engaged with the brake pin, a spring which always pushes the another end of the clutch piece toward the center axis side of the clutch case. Only when a winding speed of the screen is more than a given level, the clutch piece is moved against a spring force of the spring by a centrifugal force generated by the rotation of the winding pipe. The clutch piece is moved toward the outside direction of the clutch case and the engaging portion of the clutch piece is engaged with the brake pin. Thereby, the winding speed of the screen is decreased only when the winding speed of the screen is more than the given level. Accordingly, the winding speed of the screen is not so excessively decreased that the screen can be still wound to the end. Alternatively, a positioning mechanism may be provided to position the clutch case in an axial direction relative to the winding pipe when the screen is completely wound.
The positioning mechanism can include a nonscrew shaft which is formed integrally with the screw shaft and has no thread. The clutch case is moved from the screw shaft to the nonscrew shaft immediately before a screen is completely wound. Further, the positioning mechanism can include a push spring for pushing back the clutch case on the nonscrew shaft toward the screw shaft.
Alternatively, the positioning mechanism can include a nonscrew shaft portion which is formed at an end portion of the screw shaft and prevents the movement of the clutch case, and a clutch spring mounted inside of the clutch case and inserted between a slip ring engaged with said screw shaft and the clutch case. The clutch spring makes the clutch case idle in the winding direction of the winding pipe at the end portion of the screw shaft relative to the slip ring.
The present invention disclosure relates to subject mater contained in Japanese Patent Application No. 9-326107, filed Nov. 27, 1997, which is expressly incorporated herein by reference in its entirety.